Temperature-dependent Changes in Cardiovascular Parameters During Warm Water Footbaths in Healthy Women

Pressure Rate Product (PRP), calculated from systolic blood pressure (measured with the Mobil-O-Graph® PWA) and heart rate (measured with the Bittium Faros 360TM ECG recorder) at timepoint 5 (t5 = mean of the measurements recorded from minute 21 to minute 30 of the footbath).

Pressure Rate Product (PRP), calculated from systolic blood pressure (measured with the Mobil-O-Graph® PWA) and heart rate (measured with the Bittium Faros 360TM ECG recorder) at timepoints t1 (t1 = mean of the measurements recorded from minute 1 to minute 10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1 to minute 10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11 to minute 20 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1 to minute 10 of the post-intervention rest period).

SDNN: Standard deviation of normal to normal (NN) intervals (ms) (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

pNN50: Percentage of successive NN intervals that differ from each other by more than 50 ms (%) (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

HF: High frequency power band (0.15-0.40 Hz) (ms2) from frequency domain analysis (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

LF: Low frequency power band (0.04-0.15 Hz) (ms2) from frequency domain analysis (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

LF/HF ratio = ratio of two bands from frequency domain analysis: LF band (0.04-0.15 Hz), HF band (0.15-0.40 Hz) (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

VLF: Very low frequency power band (0.0033-0.04 Hz) (ms2) from frequency domain analysis (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Mean heart rate (bpm) (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

SD2/SD1 ratio, derived from Poincaré plot (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Stress Index (SI) according to Baevsky's formula SI = AMo/2Mo*MxDMn (Mo = mode, AMo = mode amplitude, MxDMn = variation range of RR intervals) (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Respiration rate (1/min) (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Heart rate/respiration rate ratio (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

RMSSD: Root mean square of successive differences (ms) (Bittium Faros 360TM ECG recorder). Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Stiffness Index, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Perfusion Index, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Peak to Peak Time (PPT, ms), measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

SlopeInW1, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

SlopeInW2, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

SlopeInW3, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

SlopeInW4, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Reflection Index, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

TimeTX (ms), measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

TimeTY (ms), measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

QuotTYTX, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

AreaAX, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

AreaAY, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

QuotAYAX, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

TimeTV (ms), measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

TimeTW (ms), measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

QuotTVTW, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

AreaAV, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

AreaAW, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

QuotAVAW, measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Oxygen saturation (SpO2, %), measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Pulse Transit Time (PTT, ms), measured with the Vitaguard® VG 3100 monitor, getemed, Germany. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Systolic Blood Pressure (mmHg), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Diastolic Blood Pressure (mmHg), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Mean Arterial Pressure (mmHg), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Pulse Pressure (mmHg), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Stroke Volume (ml), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Cardiac Output (l/min), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Peripheral Resistance, measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Cardiac Index, measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Augmentation Pressure (mmHg), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Augmentation Index, measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Pulse Wave Velocity (PWV, m/s), measured with the Mobil-O-Graph® PWA. Measurements analysed at timepoints t1 (t1 = mean of the measurements recorded from minute 1-10 of the pre-intervention rest period), t3 (t3 = mean of the measurements recorded from minute 1-10 of the footbath), t4 (t4 = mean of the measurements recorded from minute 11-20 of the footbath), t5 (t5 = mean of the measurements recorded from minute 21-30 of the footbath), and t7 (t7 = mean of the measurements recorded from minute 1-10 of the post-intervention rest period).

Self-reported warmth perception at both feet, assessed with the "Herdecke warmth perception questionnaire" immediately before (timepoint 2, t2), immediately after (timepoint 6, t6) and 10 minutes following the footbath (timepoint 8, t8). Each item is scored 0-4 (0 = cold; 4 = hot), yielding a mean between 0 and 4.

Self-reported warmth perception at both hands, assessed with the "Herdecke warmth perception questionnaire" immediately before (timepoint 2, t2), immediately after (timepoint 6, t6) and 10 minutes following the footbath (timepoint 8, t8). Each item is scored 0-4 (0 = cold; 4 = hot), yielding a mean between 0 and 4.

Self-reported warmth perception at the head, assessed with the "Herdecke warmth perception questionnaire" immediately before (timepoint 2, t2), immediately after (timepoint 6, t6) and 10 minutes following the footbath (timepoint 8, t8). Each item is scored 0-4 (0 = cold; 4 = hot), yielding a mean between 0 and 4.

Self-reported overall warmth perception, assessed with the "Herdecke warmth perception questionnaire" immediately before (timepoint 2, t2), immediately after (timepoint 6, t6) and 10 minutes following the footbath (timepoint 8, t8). The item is scored 0-4 (0 = cold; 4 = hot).

Self-reported well-being, assessed with the "Basler Befindlichkeits-Skala" (Basel Mood Questionnaire, BBS) immediately before (t2), immediately after (t6) and 10 minutes following the footbath (t8) (BBS: 16 items; 7-point rating scale; higher values represent a better outcome).

Self-reported footbath comfort, assessed with a 7-point face scale ranging from "very comfortable" (laughing face) to "very hard stress" (crying face).

Self-reported perception of warmth and skin stimulus during the footbath, assessed with a dynamic warmth and skin stimulus visual analog scale (VAS), applied once per minute (0 = cold/no stimulus; 10 = very hot/very strong stimulus).

Self-reported personal preference of footbath, assessed with a short questionnaire asking which footbath had the most positive overall effect (check boxes to mark for the first, second, third, or fourth footbath) and why (short, self-formulated statement of reasons). Assessed once after the fourth footbath intervention.